Lu Zuokun,
The first thing to note in the image is TOO MUCH nucleation.
To solve this you need to reduce either the precipitaant or the protein
concentration.
The larger crystals are separated from the shower. This is positive.
I suggest you use 10% PEG ME 550 instead of 16%.
If you get no crystals. after 1 day. streak seed with the crystals you
have obtained.
http://dx.doi.org/10.1016/0022-0248(91)90896-D
If after 6 hours you still do not have crystals, use a booster solution.
(i.e. 5M NaCl addition to
the reservoir of your vapour diffusion experiment.) The use of booster
solutions is described in:
http://dx.doi.org/10.1016/j.nbt.2014.09.002
When the optimization steps with your current protocol have all been
carried out, then
you should follow Prem's advice and screen additives. Screening addditives
when you have
your crystallization experiment out of control, will not give you any
positive results unless you
are lucky.
I wish you good luck, but do not rely on luck alone.
Enrico.
On Fri, 10 Apr 2015 16:42:06 +0200, luzuok <[log in to unmask]> wrote:
>
>
> Dear all,
> Sorry to ask an off-topic question.
> The molecular weight of the protein is about 40 kDa. The protein is
> an ATPase and forms monomer to oligomer (about 400 kDa) in various sizes
> in solution.
> Crystals were observed in several conditions. eg. Bicine pH 7.8, 16%
> PEG ME 550, 0.1m NaCl. But all of them show small needle form. See
> picture below.
> I was told that this kind of crystal is very difficult to optimize.
> Regular optimization method is carried out but failed.
>
>
> Does anyone have idea on optimizing this kind of crystal? Or is it
> case by case?
>
>
> Best regards!
>
>
> Lu Zuokun
>
>
>
>
> --
> 卢作焜
> 南开大学新生物站A202
--
Enrico A. Stura D.Phil. (Oxon) , Tel: 33 (0)1 69 08 4302 Office
Room 19, Bat.152, Tel: 33 (0)1 69 08 9449 Lab
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